Camp hammocks are becoming a popular alternative to tent camping because a hammock can provide a more comfortable nights sleep than sleeping on the hard ground. But that comfort of being elevated off the hard ground, with the hammock bed sagging between two trees or vertical supports, is compromised by the hammocks two inherent problems: 1) Hammocks, when used for cold weather camping and being made of a single layer of thin fabric, have no insulating quality and lack good body heat retention. Unlike a tent, which gains insulation from the ground at the tent floor, a hammock suspended above the ground allows cold air to penetrate the bottom of the unprotected hammock, 2) Most single support axis hammocks cause the occupant to lay in a recumbent position with the head, legs and feet at higher points than the torso, making it much more difficult get a full nights sleep or to lay on one's side. Many hammock designers have tried to solve these problems with some success but each has it's own limitations and disadvantages.
On the later issue, most single support axis hammock designs are based on the Mayan and/or Brazilian hammocks. It was well understood that when these rectangular shaped hammock beds were hung between two supports and allowed a given amount of sag, they functioned better if the occupant was lying on a diagonal across the suspension axis of the hammock. Distributing the weight of the occupant's body across the suspension axis and placing the head and feet at points further from the suspension points, places the body on a much flatter plane of the sagging fabric. The wider the hammock body and the higher the angle of diagonal the occupant could lay across the suspension axis, the flatter the plane would become.
In the effort to create a hammock body that did not need to be so wide but still lay flat, as if lying on a cot, some designers added “spreaders” to each end, keeping the hammock bed open, and not allowing as much sag to the hammock body (see U.S. Pat. No. 4,001,902, U.S. Pat. No. 4,021,869, U.S. Pat. No. 6,701,549 & U.S. Pat. No. 8,161,991). This can make the hammock top heavy and unstable and still does not allow the occupant to lie on a flatter plane.
Designers of “asymmetrical” hammocks understood that, like the Mayan and Brazilian hammocks, lying across the support axis of the hammock provides much more comfort and, by allowing a given amount of sag to the hammock body, the hammock would be more stable (see U.S. Pat. No. 6,865,757). The designers state that their “asymmetrical” design will, “also support the concave areas of the torso, such as the spine”. However, the weight of the occupant's body, now causing the fabric of the hammock bed to stretch on the bias of the fabrics weave, will cause the spine to bend and the hammock will now conform to that bend of the spine, not providing the support they state. What had been overlooked in their design is that the weight of the torso is much heavier than that of the legs, feet and head. So, even though the occupant is now lying on the diagonal of the hammock, allowing the body to lay in a flatter plane, the fabric's “give” under the weight of the torso will cause the legs and feet, which are not as heavy, to remain at a higher plane thus making the spine bend.
Further more, any single suspension axis symmetrical hammock, rectangular in shape or otherwise, will function better when the occupant is lying in the flatter plane of the diagonal (this was understood with the Mayan and Brazilian designs). And, once the occupant lies on the hammock, in this manner, introduces a new variable to the symmetric shape of the hammock making it asymmetric in shape when viewed from above.
Other hammock designers have designed the hammock bed in a manner that will allow a more level sleeping area while the occupant is lying along the support axis and not across it (see U.S. Pat. No. 7,020,915). This is done by cutting the fabric of the hammock bed into a shape that gives more fabric area to the head and foot section of the hammock and, once sewn together, creates a more level sleeping area. The fabric, that makes up the hammock bed, is cut so the sides of the hammock taper inward so that once suspended between two points and pulled taut, the sides keep the middle of the hammock at a higher point than both the head and foot area. These hammocks, once suspended, resemble a boat with a flat keel. The designers have stated, that by doing this, the hammock body does not need to be so wide since the occupant does not have to lie on a diagonal in order to be on a flatter plane. While this does provide a more level or flat sleeping surface, the weight of the occupant, who is now inline with the support axis, will create tension on both sides of the hammock causing the sides to tighten in around the occupant making movement inside the hammock more difficult.